The invention relates to a joint rod for a motor vehicle.
A typical joint rod comprises two joint, in particular ball stud joints, and a rod section connecting the joints. Such joint rods are used e.g. in the chassis of a motor vehicle as steering tie rods. During the driving operation, these steering tie rods are exposed to high loads and therefore have to have great rigidity. On the other hand, in vehicle manufacture there is the general demand for reducing the weight both under the aspect of saving energy and, in particular in the area of the chassis, to increase the driving comfort. Joint rods used so far usually consist of a rod section made of steel and a joint section which is mounted thereon e.g. by friction welding and comprises a turned joint socket and a ball pin, both also made of steel. The ball pin and the joint socket cannot be joined until they have been mounted by welding in order not to impair the function of the joint by the welding process.
Furthermore, it is known to make joint rods of plastic material, the rod section and the joint socket being injection-molded in one piece and then the ball pin being inserted. A certain weight reduction can be obtained with these plastic joint rods vis-a-vis the steel type, although the rod section must be realized in rather solid fashion in its middle region to achieve the required rigidity. However, the it is extremely disadvantageous in connection with these joint rods that for the production of a joint rod having another length a new tool has to be produced, e.g. for another vehicle type or in case the design of the chassis is modified.
Another drawback existing in connection with both the steel and the plastic versions consists in that the joint rod has to be handled in its entire length when the ball end is inserted, an adaptation of the handling tools being again required for joint rods of different length.
Therefore, it is the object of this invention to create a joint rod which offers weight saving over the formerly used ones and can be produced in a simple and cost-effective manner, in particular with respect to a series production of similar items with differing length.
To this end, the invention provides a joint rod adapted for motor vehicles, which consists of a joint section having a connecting surface and a rod section having an inner surface. The joint section and the rod section being joined by positive engagement between the connecting surface and the inner surface. The rod section is made from a first material and the joint section is made from a second material, the first material and the second material being different from each other. In this way, the same joint sections can be used for joint rods of differing length, which can therefore be produced in greater numbers and thus in more cost-effective manner. The production of a positive engagement does not impair the function of the joint section, so that it can be combined from the joint socket and ball pin already before being connected with the rod section. In this connection, only the joint section has to be handled which is substantially smaller than the entire joint rod and furthermore can be uniform for joint rods having differing lengths. A commercial semi-finished product can be used for the rod section in cost-effective manner, which product is cut into lengths for the joint rod to be produced in accordance with the desired dimensions. Materials which have exactly the properties called for in the respective section can be used for joint section and rod section.
According to the preferred embodiment of the invention the rod section consists of an electrically well conductive material and the joint section is made of a fiber-reinforced plastic material. Therefore, the joint section can be produced very simply and in cost-effective manner by means of injection molding and can reliably be joined in simple manner by magnetic deformation of the rod section so that the inner surface of the rod section positively engages the connecting surface of the joint.
Further embodiments of the invention and their advantages follow from the subclaims.